Cutting head for a wire cutting machine, in particular a strimmer

ABSTRACT

A cutting head for a cutting machine, in particular a strimmer, having a hub ( 4 ) connected to a drive member ( 9 ) of the cutting machine, and a number of filiform elements ( 7 ) connected to and extending substantially radially from the hub ( 4 ); each pair of filiform elements ( 7 ) being defined by respective end portions ( 7   a,    7   b ) of a single wire having a C-shaped intermediate portion ( 7   c ) housed firmly inside the hub.

TECHNICAL FIELD

The present invention relates to a cutting head for a wire cuttingmachine, in particular a string trimmer.

BACKGROUND ART

Wire cutting machines are known, which comprise a substantiallycylindrical hub, and a number of filiform elements, each comprising anend portion connected to the hub, and each extending from the hubsubstantially radially; and the hub is connected to an output shaftrotated by an electric motor or combustion engine of the machine torotate the filiform elements at high speed and so perform the desiredcutting action.

On known cutting machines, the spin imparted to the filiform elements bythe high rotation speed of the hub may be such as to detach the elementsfrom the hub, thus resulting in injury to the user.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to documents U.S. Pat. No.2,663,137 and U.S. Pat. No. 4,062,115 describe cutting heads as definedin the preamble of claim 1 provide a cutting head for a wire cuttingmachine, designed to prevent detachment of the filiform elements.

According to the present invention, there is provided a cutting head fora wire cutting machine, in particular a string trimmer as claimed inclaim 1.

BRIEF DESCRIPTION OF DRAWINGS

A preferred, non-limiting embodiment of the present invention will bedescribed by way of example with reference to the accompanying drawings,in which:

FIG. 1 shows an exploded view in perspective of a cutting head for acutting machine, in particular a string trimmer, in accordance with theteachings of the present invention;

FIG. 2 shows a top plan view of a first element of the FIG. 1 cuttinghead;

FIG. 3 shows a section of the first element along line III—III in FIG.2;

FIG. 4 shows a top plan view of a second element of the FIG. 1 cuttinghead;

FIG. 5 shows a section of the second element along line V—V in FIG. 4.

BEST MODE FOR CARRYING OUT THE INVENTION

Number 1 in FIG. 1 indicates a cutting head for a wire cutting machine,in particular a string trimmer. Head 1 comprises a hub 4, and a numberof filiform elements 7 fitted to and extending radially from hub 4; andhub 4 is connected to an output shaft 9 rotated by a motor—e.g. anelectric motor or combustion engine (not shown)—of the machine to rotatefiliform elements 7 at high speed.

More specifically, hub 4 comprises an axially symmetrical first body 11having seating means for housing filiform elements 7; and an axiallysymmetrical second body 14 connectable to first body 11 to firmly clampfiliform elements 7 inside the seating means.

With reference to FIGS. 2 and 3, first body 11 comprises a substantiallydisk-shaped base portion 17; and a cylindrical tubular wall 19 extendingintegrally from a flat face 21 of base portion 17 and coaxially with anaxis 23 perpendicular to face 21. Wall 19 has an outside diameter dsmaller than the diameter D of base portion 17, is defined externally bya cylindrical surface on which is formed a thread 26, and comprises anumber of radial slots (six in the example shown) 28 equally spacedangularly about wall 19 (FIG. 2) and extending the full height h of wall19 (FIG. 3). Each slot is defined laterally by two facing surfaces ofwall 19, and at the bottom by a portion of face 21; and first body 11 isconveniently molded from plastic material, e.g. nylon.

With reference to FIGS. 4 and 5, second body 14 is substantiallycylindrical, is defined by a cylindrical lateral wall 29 and by twoopposite end walls 30, 31, and defines an inner cylindrical cavity 32coaxial with axis 33 and communicating externally of body 14 through acircular opening 34 in wall 31. Cylindrical cavity 32 has a diametersubstantially equal to diameter d, and is defined laterally by acylindrical lateral wall having a thread 37, and by a flat bottom wall39 perpendicular to axis 33; and a cylindrical opening 41 extendscoaxially with axis 33 from bottom wall 39, communicates externally ofbody 14 on the opposite side to opening 34, and provides for housingoutput shaft 9 in angularly fixed manner.

Each pair of filiform elements 7 is defined by respective end portions 7a, 7 b of a single wire comprising a C-shaped intermediate portion 7 cfitted firmly to hub 4. More specifically, intermediate portion 7 c isfitted inside wall 19, and engages two adjacent radial slots 28 (FIG. 2)from which the wire comes out with end portions 7 a, 7 b outside wall19; the sector of wall 19 between the two adjacent slots 28 acts as aradial stop for intermediate portion 7 c; and second body 14 isconnected to first body 11 by screwing wall 19 inside cylindrical cavity32 to grip intermediate portion 7 c of the wire between face 21 and wall31. In which position, intermediate portion 7 c of the wire is connectedfirmly to hub 4 by the pressure exerted on the wire by bodies 11 and 14,and, even when hub 4 is rotated at high speed, detachment of thefiliform elements is prevented by intermediate portion 7 c being firmlyhoused inside wall 19 by the connection of bodies 11 and 14, and beingprevented from moving radially by the constraint defined by the sectorof wall 19 between the two adjacent slots 28.

Clearly, changes may be made to the cutting head as described andillustrated herein without, however, departing from the scope of thepresent invention.

What is claimed is:
 1. A cutting head hub for connecting to a drivemember and receiving a number of filiform elements of a string trimmer,the filiform elements each having an intermediate portion with oppositeend portions extending substantially radially from said cutting headhub, said cutting head hub comprising: an axially symmetrical firstbody; and an axially symmetrical second body for seating with said firstbody and clamping said filiform elements, wherein said axiallysymmetrical first body comprises at least a tubular wall having a numberof angularly spaced radial slots for receiving said intermediate portionof each of said filiform elements at least partly inside said tubularwall and engaging two of said radial slots from which said end portionssubstantially radially extend; wherein said axially symmetrical secondbody comprises at least a cavity for housing at least partially saidtubular wall and an end portion for clamping said filiform elements; andwherein said tubular wall is defined externally by a cylindrical surfacewith a thread for said clamping of said filiform elements.
 2. Thecutting head hub as claimed in claim 1, characterized in that said firstbody comprises a substantially disk-shaped base portion and said tubularwall is cylindrical and extends in one piece from said base portion andcoaxially with an axis transverse to said base portion.
 3. The cuttinghead hub as claimed in claim 2, characterized in that said tubular wallhas an outside diameter smaller than a diameter of said base portion. 4.The cutting head as defined in claim 3, characterized in that saidradial slots extend the full height of said tubular wall.
 5. The cuttinghead as defined in claim 2, characterized in that said radial slotsextend the full height of said tubular wall.
 6. The cutting head asdefined in claim 1, characterized in that said radial slots extend thefull height of said tubular wall.
 7. A cutting head for a stringtrimmer, comprising a hub for connecting to a drive member of saidstring trimmer; and a number of the filiform elements fitted to andextending substantially radially from said hub; each pair of saidfiliform elements being defined by respective and portions of a singlefiliform element of said number of filiform elements; said hubcomprising an axially symmetrical first body, and an axially symmetricalsecond body connected to said first body, characterized in that saidaxially symmetrical first body comprises at least a tubular wall in turncomprising a number of angularly spaced radial slots; an intermediateportion of each of the said filiform elements being housed at leastpartly inside said tubular wall, and being positioned with each of thesaid filiform elements engaging two said radial slots and with said endportions outside said hub, said first body having a disk-shaped baseportion, said tubular wall being cylindrical and having an outsidediameter smaller than the diameter of said base portion thus forming alip on said base portion, said to tubular wall having an exteriorthreaded surface for screwing into a cavity on said second body, an endportion of said second body cooperating with said lip to clamp saidfiliform elements.
 8. The cutting head hub as defined in claim 6,wherein said angularly spaced radial slots extend a full height of saidtubular wall.
 9. A cutting head hub for connecting to a drive member andreceiving a number of filiform elements of a string trimmer, thefiliform elements each having an intermediate portion with opposite endportions extending substantially radially from said cutting head hub,said cutting head hub comprising: an axially symmetrical first body; andan axially symmetrical second body for housing at least part of saidfirst body and clamping said filiform elements, wherein said axiallysymmetrical first body comprises at least a substantially cylindricalcoaxial tubular wall having a number of angularly spaced radial slotsfor receiving said intermediate portion of each of said filiformelements at least partly inside said tubular wall and engaging two ofsaid radial slots with said end portions substantially radiallyextending; wherein said axially symmetrical second body comprises atleast a cavity for said housing of at least part of said tubular walland an end portion for said clamping said filiform elements, at leastone of said cavity and said part of said tubular wall having a screwthread cooperative with the other of said cavity and said part of saidtubular wall for said clamping; and wherein said axially symmetricalfirst body has a disk-shaped base portion, said tubular wall projectingcoaxially from said disk-shaped base portion and having an outsidediameter smaller than a diameter of said disk-shaped base portion forforming a lip for said clamping.
 10. The cutting head hub as defined inclaim 9, wherein said angularly spaced radial slots extend a full heightof said tubular wall.